Damage modeling of hot mix asphalt under repeated loading

Fatigue damage is one of the primary distresses in hot mix asphalt (HMA) pavements. The complex viscoelastic behavior of the asphalt composition poses challenges in developing robust models for predicting fatigue life and assessing damage. This study aims to explore a relatively direct model to address these challenges. A continuum damage mechanics (CDM)-based model is applied to HMA, in which dissipated energy is defined as the damage variable, while temperature and strain are considered dependent variables. By defining damage in terms of dissipated energy, rather than the conventional approach of tracking the degradation of the stiffness modulus, the model can be calibrated to provide reliable fatigue life predictions. Furthermore, such a model addresses key limitations associated with stress triaxiality and enables direct exploration of the variables governing fatigue damage. Fatigue curves, obtained from repeated loading in four-point bending tests under strain-controlled conditions, are used to calibrate the model’s coefficients. The model is verified through experimental investigation, demonstrating good agreement between the predicted and measured damage evolution and fatigue life, even at relatively high temperatures. The results quantitatively demonstrate that fatigue life increases with the increase in temperature and decreases in high tensile strain levels. Moreover, it is found that temperature plays a key-factor in determining the coefficients of the fatigue damage model. This finding enables the determination of model coefficients for HMA using a limited number of flexural fatigue tests conducted in constant-strain mode. The proposed model’s methodology can be applied to evaluate the fatigue life of various HMA compositions. • The study presents a CDM based model for assessing the fatigue life of HMA. • Dissipated energy is defined as the damage variable. • Model coefficients are calibrated using fatigue curves from 4PB test experiments. • Temperature is a key-factor in determining the coefficients of the damage model. • The proposed direct fatigue damage model can be applied to various HMA mixtures.